Doctor blade



March 16, 1943. A. E. LUNDBY'E DOCTOR BLADE Filed June 2, 1942 g] 1 wbnfm,

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Patented M... is, 1943,

UNITED STATES PAT N ()FFIGE 2.313.330 l f t e i fhio, assignort The OrowelI-Oollier Publishing Company.

fSpringiield. ()h io, a corporation of Delaware Application June 2, 1942, Serial No. 445,481

' a claim. (01. 101-169)! My invention relates to new and usefulimprovements in doctor blades, and the present application isa continuation in part of an application illed by me on September 9, 1941, Serial No: 410,205; for doctor blades.

As is well known to. those skilled in the art. a

' doctor blade is a thinsteel knife which is used to scrape off the excess ink which is sprayed on an intagliated printing cylinder, commonly known as a rotogravure printing cylinder.

- Heretofore most doctor blades have been made from a high carbon content pure Swedish steel v which at the present time is impossible to secure.

One of the objects of the present invention is to provide a doctor blade that is so made that it will function well for at least 700,000 or 800,000

revolutions of the cylinder before the blade has to be removed and resharpened, and at the same time will have less tendency to scratch the cyl-' inder than heretofore has been found possible with the present form of doctor blades now in use. 0 Still another object of the invention is to'providea new and novel'formof doctor blade that may be chromium plated along its forward edge but not necessarily throughout its entire length, as, doctor blades generally are unsupported near their opposite ends,'.and as the blade about to be described may be somewhat brittle it is pref erably plated therefore only throughout its supported portion.

Still another object of, the invention is to provide a doctor blade that may be plated and heat treated asset forth in the application hereabove referred to, and to further provide a means of lubricating the blade to thus overcome any tend- .ency to scratch the relative soft cylindrical printing surface of the rotating printing cylin- Still another object of the invention to provide a doctor blade of what .might be termed i a laminatedstructure- -that is,.between the two vent the scratching of the soft copper face of tion of the rotogravure or intaglio printingcy'lintherotating cylinder while the same is being scraped. 5 Still another object of the invention is to provide a lubricated doctor blade which will thus prevent any tendency for the blade-to wear unevenly, .to thus form spots or edges'which tend to. scratch the intagliated surface of the cylin- 'der.

-With these and other objects in view, my invention consists in certain new and novel arrangements and combination of parts as will be hereinafter more fully described and pointed out in the claims. v

Referring now to the drawing showing a preferred embodiment 'andt'wo slight modifications,

Fig. 1 is a fragmentary view of a doctor blade holder,together with my improved doctor blade supported therein, the dot-and-dash line showing a fragmentary portion of the rotating printing cylinder, and the doctor blade being in a raised position for the sake of clearness of illustration;

Fig. 2.-is an enlarged fragmentary portion of the improved doctor blade showing the lubricating fllmcompressed between" the two sheets of the doctor blade, taken on line 2-4 ofv Fig. 1, the supporting \plates omitted for the sake of clearness; a

Fig. 3 isa similar fragmentaryrportion of a slightly modified form, showing the lubricating compound as secured to, the upper surface of the blade; a

. I Figure 4. is a similar view tov Fig 3, showing another modified form where the lubricating compound is pressed on the under surface of the blade; and f Fig. ,5 is an enlarged fragmentary sectional view of the forward edge ofthe blade showing thescraping angle and also showing-the blade as being chromium plated along its forward edge.

Referring now more particularly to the several views, and for the moment to Fig. 1, there is fragmentarily shown the ,ddctorblade assembly wherein there is a holder A for the sector blade about to be described, anda holder B-for the backing blade 0; which contacts one i (the lower) of the plates 1). between which plates is secured my new and improved doctor bladeE.

There may 'also be seenthe' fragmentary porder F, on which the forward edge of the blade E v rests when in its functioning position to scrape oil! the excess ink from the said rotating printing cylinder F. Y a Y length if desired.

' April 1 1942, Serial No. 437,270;

A doctor blade generally consists of a thin blade of steel of from two thousandths of an inch the doctor blade is reciprocated axially of the cylinder to thus prevent any rough spots that may form on the blade from cutting a track or scratching the cylinder.

The present blade is preferably chromium,

plated on its forward edge as at G (Fig. 5) and the plating may terminate, if so desired, short of its opposite ends. It might be mentioned that the ends are generally unsupported, and by stopping the chromium plating short of the ends which are not used for scraping, there is less likelihood of the blade fracturing at these unsupported ends.

However, it will be understood that the chromium plating may extend throughout its The chromium plating of the blades per se does not form the gist of the present invention, as this is set forth in the application previously mentioned by me, and it will be understood that I can use the present doctor blade without electroplating the same, if so desired, although it will not, of course, give near the length of service as if the blade is plated in accordance with themethod set out in an applicationfiled by me on The forward edge of the blade is preferably cut with a wiping angle of approximately as atK (Fig. 5) although here again the angle may be changed if so desired.

Thus far, the doctor blade assembly referred to is similar to that heretofore mentioned, but in the present instance, as may be seen by Fig.2,

This'lubricating compoundmay be a graphite,

I and may have a binder therein, such as bitumen,

or any other desired adhesive, so that it may be slightly heated and then compressed between the blades to thus securely hold the compound in place between the two metal sheets.

It is well known that the ink used in printing with rotogravure presses has no lubricating qualities, so that it often happens that the steel:

doctor blade will wear unevenly and the edge become rough, comparatively speaking, so that the I provide a lubricatingmedium as a part of the sheet as in the preferred'form, I compress the graphite 5 directly to the upper surface of the plate 4, so that in this instance the lubrication is on the top surface of the blade, rather than in between two sheets that make up the blade.

Referring now to Fig. 4 showing the final modifled form there is the one sheet of thin steel 6, and the graphite I is secured along the wider surface of the blade.

Thus in all three instances the doctor blade, whether consisting of one sheet of steel or two, is provided with its own lubricating compound to thus prevent the hard metal of said blade from scratching or wearing the copper cylinder.

It will be understood that as heretofore mentioned, the forward edge of the doctor blade is preferably coated with chromium to provide a hardened surface, and other metals might be used for the coating, such as nickel; but the blade 1. A doctor blade for printing presses, including a relatively thin metal strip having its forward edge ground to a sharp wiping edge, and a lubricating compound secured to the blade and forming a part thereof, to thus lubricate the blade as it bears against the rotating printing cylinder of a printing press.

2. A doctor blade for printing presses, includinga relatively thin metal strip having its forward edge electro-plated and ground to a sharp wiping edge, and a lubricating compound secured to the blade and forming apart thereof, to thus I v lubricate the blade as it bears against the 'rotating printing cylinder of the printing press.

3. A doctor blade for printing presses, including a relatively thin metal strip having its forward edge sharpened and a lubricating compound compressed on the blade and forming a part blade riding against a soft. surface,'that is, a soft copper shell on which are the intricately etched designs for the rotogravure print-has a tendency to'cut minute grooves in the coppershell, and even though these grooves and nes are so minute that they are hard to see with the naked eye, they still subtract from the printing'value.

However, I have found thatby using a laminated form of blade 'whichis provided with a lubricating compound, the doctor blade will scrape off the excess ink on the cylinder and will prevent both the-wearing and scratching of the cylinder, and at the same time lubricate the hardened plated doctor blade to thus prolong its use without resharpening.

In the modified form'as shown in Fig. 13, will be seen a single steel sheet 4 and in this instance, rather than using an additional or upper thereof, to thus lubricate the blade as it bears against the rotating printing cylinder of the printing press.

4. A doctor blade for printing presses, including two relatively thin metal strips, their forward edges being ground to provide a sharp wiping edgefa lubricating compound compressed between the two sheets and forming a part thereoilto thus lubricate the blade as 'it bears against the rotating printing cylinder of theprinting press.

5. A doctor blade for printing presses, including two relatively thin metal strips havingtheir forward portions ground to a sharp wiping edge,

.the said forward edges also being chromium plated, and a relatively thin layer of lubricating I compound compressed between the two sheets and forming a part of the blade to thus lubricate the blade as it bears against the rotating printing cylinder of -the printing press.

6. A doctor blade for printing presses, including a relatively thin metal strip having its for ward edge ground to thus present a sharp wipmg edge,'the forward edge also being chromium the under surface ofthe blade to thus lubricate 10 the blade as it bears against the'rotati rinting cylinder of the printing press.

8. A doctor blade for printing presses, including a thin metal blade and a graphite compound having an adhesive mixed therewith, and the compound coated on the blade and forming a part thereof, to thus lubricate the blade as it bears against the rotating printing cylinder of the printing press.

' AXEL E. LUNDBYE, 

